1. Field of the Invention
The present invention relates to an apparatus and a method for communication between sending and/or receiving stations and a transfer station, wherein the sending stations supply the transfer station with data intended to be carried further to the receiving stations, and the transfer station takes over the data supplied to it and carries the data directly or indirectly to the particular desired receiving station.
Such known apparatuses and methods will be described briefly below by taking the ATM method as an example.
As early as May 1990, the CCITT (Consultative Committee for International Telephony and Telegraphy) made the ATM (asynchronous transfer mode) the standard for so-called data packet transfer in the B-ISDN. ATM was defined as follows: "A transfer method in which the information is bundled in cells; the method is asynchronous in the sense that the cells need not necessarily be exchanged periodically between the sender and the receiver. "
According to one possible embodiment for performing the ATM method which is shown in FIG. 2 and described below, a transfer station in the form of a so-called ATM layer circuit, and a plurality of sending stations in the form of so-called PHY layer circuits, are provided. The plurality of sending stations are connected to the one transfer station and transmit asynchronous data packets (cells) to it, which are intended for further conduction or transfer to receiving stations.
The transfer station has a maximum data throughput that cannot be exceeded. Consequently, the sending stations must in principle be constructed in such a way that, or only so many sending stations can be connected to a transfer station so that, the sum of data quantities transmitted per unit of time to the transfer station does not exceed the maximum throughput of the transfer station. However, in some sending stations, the quantity of data to be transmitted per unit of time to the transfer station can vary sharply, for instance if the sending station is a terminal or the like, or if the sending station is connected to such a device.
If in such a case the basis for the layout and/or adjustment of the system is made to be the maximum possible quantity of data that can be transmitted in an extreme case from the particular sending station to the transfer station, then as a rule only extremely seldom is the transfer station appropriately utilized. In most cases, it is instead operated far below its performance limit. The procurement and operation of such a system would therefore be relatively expensive.
On the other hand, if the basis for the layout and/or adjustment of the system, to increase economy, is not the maximum amount of data transmissible from the particular sending station to the transfer station but rather only a lesser quantity of data, such as the average amount of data to be transmitted, then it can happen that the transfer station is supplied with more data per unit of time than it can pass on. As a consequence, data sent to the transfer station can be lost. Under some circumstances, operating a system constructed in that way would thus involve a not inconsiderable risk to security or safety.
None of the aforementioned options is satisfactory.